Aircraft cabin air conditioning system and control valve therefor



Aug. 7, 1951 w. M. HYNEs 2,562,918

AIRCRAFT CABIN AIR CONDITIONING SYSTEM AND CONTROL VALVE THEREFOR Filed Feb. 9, 1949 4 Sheets-Sheet l Aug. 7, 1951 w. M. HYNES 2,562,918

AIRCRAFT CABIN AIR CONDITIONING SYSTEM AND CONTROL VALVE THEREFOR Filed Feb. 9, 1949 4 Sheets-Sheet 2 INI/ENTOR. WML/HN /V HWS/E5 Aug. 7, 1951 w. M. HYNES 2,562,918

AIRCRAFT CABIN AIR CONDITIONING SYSTEM AND CONTROL VALVE THEREFOR Filed Feb. 9, 1949 4 Sheets-Sheet 5 BY Manif-1 a Aug. 7, 1951 w. M. HYNES 2,562,918

AIRCRAFT CABIN AIR CONDITIONING SYSTEM AND CONTROL VALVE THEREF'OR Filed Feb. 9, 1949 y 4 Sheets-Sheet 4 Patented Aug. 7, 1951 AIRCRAFT `CABIN AIR CONDITIONING SYS- TEM AND CONTROL VALVETHEREFOR William M.'Hynes, La Grange, Ill.

Application February 9, 1949, Serial No. '75,461l

'9 claims. (o1. .9s- 1.5) i

` (Granted under the act of'lMrch s, 1883; as. 'I

amended April so, 192s; 37o o. G. 757) The inventionv described herein may be manufactured and used by or for the United States Government for governmental purposes Without vpayment to me of any royalty thereon.v

The present invention relates to' `an air conditioning system .for aircraft and to a flow control valve forming fa necessary part of the system.

-Theprimary object ofthe invention vis to provide a'system and' apparatus for use in pressurizing and airconditioningy aircraft cabins in which temperature 'responsive' control means is adapted to effect close control over the air temperature Within' the cabin and lsimultaneously maintain suiiicient flow of fresh air to maintain a minimum air pres'surein the' cabin. l

A further object ofl the invention is to provide a systemfor pressurizing and Vair conditioning the cabins of ljet propelled aircraft and `to make use of the flow `of high .pressure air from the engine air compressor to heatv the cabin, orto cool the-cabin 'after 'passing some4 of the Iair through a cooling unit, and to simultaneously supply enough air to the cabin to make up for leakage to the outside in rareed atmosphere.v

Another object of the invention is to provide an air conditioning system for an aircraft carrying an air compressor and to incorporate in said systema iiovv control valve toproportion the relative amounts of. heating and cooling air passed into the' aircraft cabin so as to maintain a cabin air temperature conducive to comfort.

-Anotherobject of the invention is to provide an air conditioning system for an aircraft carrying an air compressor and to incorporate in. said systerna` flow control valve having separate valves for the cold side and-hot side of the'air vconditioning system and to provide a" common `actuating mechanism for theseparatevalves so arranged thatfor minimum open positions of either valve the'other valve Will also be partly open in order to'maintain a minimum rate of air flow at all times for effective cabin pressurizing. f1 Another object of the vinvention is `to provide an airconditioning system for aircraft of the jet propelledl type including yan air compressordijrectly coupled to. thejetv power plantwvherein a portion of the compressed air fromv said compressor isused'to air` condition the aircraft cabin and wherein there is a iiow control valve includ,- ing a hot air control using 'two valves in series, with the iirst valve being responsive to airpressure on one `side thereof to regulate the flow of hot air therethrough and maintain a constant pressure on-the onerside of the first valve in order to maintaina: constantinlety pressure` QI! 12h@ days, lmust be reckoned with also.

second *valve and thusp rmit accurate control over the flow of hotvair by the second valve.

Anothenobject. of the invention is to provide a completely automatic air conditioning and cabinpressurizing system for jet propelledair.- craft, including flow control means adaptedto make economical use of the compressed air di,- verted from the air lcompressor of the jet Vpower plant.

Another object of. the invention is to provide an automaticY air. conditioning and cabin pressurizing system for aircraft cabins and to provide a control valve v for the system giving an improved coordination: .between the air ow along the hoi-side andcold side of the system.. y

Anotherobject of: the invention is to provide an improved valve for use in an air conditioning system and including a coordinated action for control of .air iloW alongthe hot side and .cold

side of thesystem. p 1 l -The above .and other'` objects of the invention Will becomeapparent upon reading the follow,- ing detailed `description in conjunction with the drawings, in which:v y

vFig; lis a schematic. diagram of the Ipresent air conditioning system asapplied to an aircraft havingan enginedrivenair compressor and includingja closed cabin to be heated, cooled and pressurized. H Fig..1ais a graphical representation of the valve actiongpof the.. present system to illustrate theA overlap relation ofthe valves in the hot side and cold side of the system.. z

, Fig. 2 is awiring diagram of the electrical control circuit lWhich ,is suggested vfor use inthe present air conditioningsystem. Y c Fig. zaisa wiring diagram of the bridgeY circuit forming part of the complete circuit of Fig. 2. Fig. 3 is atop plan view of the flow control valve forming anecessary and vital part of the present air conditioningl system. p

Fig. 4 is a cross sectional view 4 4 of Fig. `3. 1 Inf modern jet propelled aircraft thespeeds have reached and passed the 500 mile anhour range and it has beenfound that cooling ofthe cabin is imperative. because friction lbetween the taken on line aircraft and theaircauses heating of the aircraft skim Oftherheating loads, such as electrical equipment in; the cabin and sun load on clear `in @01d @1ilmates and also at high altitudes cabin heating may be required .instead I.of cooling land in addi:- tion high .altitudeVV requires cabin pressurif/iation -to maintain comfort and joxygen requirements.

Thus a complete cabin air conditioning system should have provision for supplying outside air to the cabin in proper quantities for cabin pressurizing when needed and the air should be supplied at the proper temperature to maintain good comfort -conditicns in the cabin. Furthermore the control of the air conditioning :system should be completely automatic in order to relieve the pilot or other personnel of unnecessary duties. Heating of the cabin is usually asimplmmatter but cooling is not so easily accomplishedi '.It.- is usually considered desirable to maintain cabin temperature below 90 Fahrenheit Abutrthisstem perature is often exceeded in practice.

Air conditioning and pressurizing system The present system of airconditioning is shown schematically in Fig. 1, Wherein-thefengine compresser is usually the turbo-compressor directly :coupled to ,the combustion` turbine of the turbojet-engine. Only a `small part of the available compressed airis `bled fromtheompressor to :accomplish thercabin airconditioning and presfsurizjing, the maior portion of'A the compressed .air

being: used to Support .combustion in the :jet engine vand thus ndrive the combustion turbine there- Kci'. jflhe compresseclhair `asbledfrom the `engine A trani-.lie air now/,tothe cutlet ducts'B and 'C so ias to result inthe proper degree oi' cooling and y heating of the/aircraft cabin. 'j Theair pathv to `thelcrabinby duct C provides a bypass aro'undrthe vair eenling u nitnand-'thus allows hot gair; to reach the cabin directlyV from the/engine compressor. Air reaching the cabin through theiduci'Bl must pass/ thrpugh a cooling `unitA and.- such; ,cooled air Emy'1`-xeol with` any concurrent ow through fduct `A`(lin the singlemduct Mj `leading into the cabin. TThe cooling unit may take any of severaldiflerent forms: but therpreferable type of `a-i'rfcooler Uor efrigerator operates on anY air cycle andiin- .dudes an expanden turlrilen 'adapted t0 extract energy from the inceming air'andgthus'cause ,rapid cooling thereof. While'this typeofl cooling unit in sizes suitableior carrying on an Aaircraft is arecent development, a rairlyrcqmplete descripytien vtljiereoi Amay befound in;.4 lviationforthe lmor-1th `of February "1947, .gpages 'i9v to152,.the larticle beingentitled fjiir condition-ing turbinevpropelledaircraft andtljierauthor' being H. J.

Wood. For the purposecffthe.present invention disclosure the ccoling unitmay' be regarded vas .cooling A.of c the cabin.

` Allairsentering.thevcabin by Way of themixing .,du'ct M aids inlmaintaining a ,desirable-cabin' air @pressure but in the event thatthe aircraft is at levels the cabin pressure might become too Ahigh. For this reason and' also to prevent too' largewa pressure diferencebetween Ainside and To Aside pressure atrhigh altitudes, the Acabin wall videdat onepoint with an automatic pressmje .reliefyalveor saetyvalYe. These AValves-are well-known, one example being that showirn the 4 patent to Cruzan No. 2,451,278. One important function of the pressure relief valve is to prevent undue stress on the aircraft walls tending to burst the cabin open. In a typical fighter aircraft the pressure relief valve is set to open when fthei-cabirr:pressure exceedsthe` outside Sair pressure by .more than six -inches of mercury. The

automatic operating means for the valve is arranged to be responsive to the pressure dierence lo. between ther cabin interior and the outside air.

.,L'Imaddition itgshould be noted that there Will be constant leakage through various crevices and lontsrasgflong as the inside pressure is more than the outside pressure, 'Ihls loss is unavoidable, lalthough `it should 'be kept at a minimum so that ltheamount of compressed air necessary for the air conditioning system may be held to a necessary minimum; Thrflow control valve is responf'siveftotemperatu're conditions in the cabin and also outside air temperature to regulate the rela- -tive 'amounts .of Y.cold and warmrair rfed into `the vcabin. `To effect this vcontrol Vvarious arrangements are .possible but the -one chosen for illustration includes two temperature sensitive resistors; or thermistors, in the"cabin Aas Vat T-I zand `T-- 2. These `elements are vpreferably placed on.or;close1tozthe pressurerelief valvewhere they are affected-.bythe :temperature ofrthe air-near its-.point ioffexit fromthecabin or acockpit. In `addition. anV outside Icompensatingelementvv or T'thermistor. T`3 isl'ocatedzinithe outside atmosphere, lpreferably inthe Ycompressor air intake, Vwhere changes in fthe :temperature-of the atmos- .fpherefwill aiect Lthe 'resistance fof fthe element. The thermistors.- T-I 'T-Z'and T-3 are Icon- -nected into a :bridge circuit was. `:represented in "Fig l bythe control unit, thecircuit effecting voperation ofi the nservomotor. I^to"control `the proper proportioningoffwarmand'cold air to =the cabin. "The circuit`I by which.thisis'accomplished will ;be described below,z :including also a `pilots temperature control: potentiometerP-2 which is manuallyl adjustablel to suit individualV comfort or climatic variations.

"'Theiow' control valve which-'is 'the heart of the present air conditioning andpressurizing sys- Vtem includes a valveD opening from the duct A into' thek interim pressure chamber 2 and controlled by a bellows i or; other pressure 'responsive Vdevice 3 connected .tot thecha'mber 2 by a tube 2'. *This valve maybe tennedamass flow convtrol` valve, since by' virtueoflits actuating means and' positioning ,in the V valveassembly it functionsto prevent increased. 'owof warm air to 'the `cabin with increased Ipowerf'setting or increased ,aircraftespeed This valvefalso makes 'it possible tomaintaincontrolover cabin'pressure by temperature"responsivemeansfalone; ksuch as thermistors T-I fand'v T-2 and-tlie circuit controlled thereby. The 'valve Tassembly also Aincludes-valve Efgoverninghotside Aair now (duct C) f and' 'valveF governing'ccldrside: airflow (duct B). 'These'two valves .areinterconnected mechanically and'positioned 'by the: servomotor i. The -in'terlinkingfs ofi suchfa character as to 'cause van overlap during-partofthe travel lof each valve. This overlap is designed to assure pressurizing' air flow at load points when thermal ,requirements Ydictate lower flows than actually 'are required to overcome or counteract cabin air leakage. Obviously Athe minimum valveove'rlap consistent -with the necessarypressurizing flow is desirable Vin'order to avoidwastin'g eng-ine compressor air. By overlap is meant the opening ofone 'valve 'fat 715 least te fsome' extent 'fbeforefcomplete closing fof aseacis thefother valve,` so that there will' always be at leastg a minimum airowinto the aircraft cabin. The means for obtaining the overlap function in atypical flow control valve as well as Athe details ofthe'valve itself will be described below. The

valveoverlapmay be shown graphically by a simple diagram as in Fig. la, wherein the ordinate axisy) is graduated in terms ofeilective. valve -area at the hot side valve E and the abscissa axis (1:). is graduated in terms of effective area at .the cold side valveF. Assuming for illustration Athat the cold side valve F is wide open, it will be vseen that the effective area is 3.2 square inches vandy.that thehot side valve area is now zero. Following the :c axis yto the lef-t it will be seen :that .the cold sideopening is reduced until it reaches 0.4 of a square inch. Now 4by following ythe line :ry upwardly it will vbe seen that the cold side valve F is still closing but at the same time .the-hot side valve E is opening. At a hot side valve` opening of 0.4. of a square inch thecold side valve will be completely closed but further voperation of the valve servomotor I in the same `direction, will further open thehot side valve E untila maximum opening of 1.4 square inches is reached.. These characteristics for the example .here given may be seen at any point along the Aheavy-line formed by portions of the r and y -axes and kbythe sloping. line ry. This dia-gram (Fig; la) represents only. one possible valve design and was arrived at after calculation of many vfactors,` such as cabin leakage, cooling load under extreme conditions,- heating load under extreme conditions, yair pressure and temperature available forthe system and determination of pressure drops to nbe expected at various parts of the system. Other satisfactory solutions may be made but for one particular installation the dia- .gramo Fig.4 1a represents `a practical design for 4a singlefengine aircraft. l.The valve areas stated are theeiective valve areas,.which are the actual yareas multipliedby a coefficient depending on the-type of valve.V` By-reading tozthe left and downwardlyfrom any point on the sloping line my `it ispossible toY determinaquickly the valve ,areas for thehot sideandv-coldside for any point in the valve overlap range. The valves D and E .in the hotside of the,` system are'preferably of the poppet type in iorder to loe substantially air tight when closed, :while the ooldside valve F.

maybe a simple butterfly valve because it is desirable to allow air leakagein the closed position and thus keep the high speed expansion turbine inthe; cooling unit running. This turbinemay .rotate as high as 100,000 R. P. M. and if lreptin Voperation..it may Aaccelerate much more quickly when thereisademand for cooling air.` In fact ii"` theturbine unitvverev suddenly accelerated .froma dead stop .thereavould probably be failure of bearings and other elements. To insure a iiow ornthe lcold side at all times regardlessof the position of lthe valve F; it is `preferable'to drilla :small vhole in the damper; element of the cold side valve F. Thus the'expansion turbine in the cooling unit will always be turning over and will be more readily accelerated when the valve F is opened by action of the electric servomotor I. Of course when the valve'F 'is closed, most of the compressed air owing from the engine compressor throughduct A must pass through `the poppet valves DandE and ductvlC, thus bypassing the cooling unit andrgivin'g a maximum cabin vheatingeffect. Forthis'reason the hot side of thefsystemmay also be termed the hot airbypass of'ithe system. Onthe cold side the airflow is 6u regulated by the valve F and also by the cooling unit, which hasv characteristics similar to an orifice whereby air now is dependent on the pressure drop available across the unit.

Valve control circuit The control unit of Fig. 1 is indicated at Uin Fig. 2, while the portion of Fig. 2 indicated at R includes the servomotor I, two limit switches .SW-I and SW-Z and a follow-up potentiometer P-. Also depicted in Fig. 2 are the similar cabin thermistors T-I and T-Z, the outside compensating thermistor T--3 and the pilots temperature control potentiometer P--2. YThe purpose of these units and components is to provide automatic and accurate control of the cabin temperature by proper actuation of the valve controlling servomotor I. The -inotor I is a split-field' reversible direct current motor including two field windings W-I and W-Z connected together at one end and leading to ground through the armature. The other endsof the two windings extend to contacts on a pair of limit switches SW-I and SW-Z adapted for actuation-by a cam G driven from the motor I through a gear reduction. .These limit switches stop the motor when the hot side and cold side valves reach their extreme open positions. For instance with the control system calling for more heat in the cabin, the winding W--Z will become active through action of the control circuit U. This will rotate the motor counterclockwise to cause the hot side valve to open and the cold side valve to close. I f the system continues to callfor more heat, the

" motor will continue to run until the hot side valve reaches maximum vopen position and the cam G opens the switch SVV-2, thus breaking the power circuit to eld winding W--2. Conversely if the control system calls for cold air, the iield Awinding W-I will becomeactive through action of the control circuit U. The motor I Ywill now run in a clockwise direction to open the cold side valve and close the hot side valve. y If this action pro ceeds to an extremeopen position for the cold side valve.' the cam G will open the limit switch SW-I to break the circuit to eld winding W-I. The motor I is also adapted to drive the follow-up potentiometer P--3 in such a direction as to rebalance the bridge circuit which governs the action of control unit U. This potentiometer is driven by the motor I through a gear reduction and thus acts to slowly cancel out the motor` actuatingv .signal of the bridgecircuit by the time the Vmotor has operated the flow control valve i sufliciently to correct thel cabin temperature.

4This follow-up action of themotor driven potentiometer P-S stabilizes the present air conditioning system and prevents wide variations in cabin temperature due to over-control and hunting This follow-up device also prevents excessive op; eration of the servomotor I, to keep wear at a minimum. I Y `The two similar and similarly :positioned ther.- mistors T--I and T-Z sense cabin air temperature, preferably at the air escape or relief valve. These elements are resistors having. a negative coeflicient of resistance, that is their resistance increases as the temperature decreases.` They may be wound resistors using wire of an aluminum alloy known as'Ohmax or may-tbe made of graphite rods which also have a pronounced negative coefficient of resistance.` The outsider air compensator T-3 is also athermistor, or ternperature responsive resistor, but this element has ill'give closer controllover the cabin temiid inorejeconoinical operation of Ythe yste'm- As'an @Kamele Consider the vaircr'aftjatfildfeet altitude vand outside air at such af temperature that cabin cooling is needed. vNow :the cold sidefa'ir path will be. open by Way of valve vRat least partly 4open anyway. kNow if the aircrtfis'sddenly'put in a. steady climb to about 1000G feet, the air temperature twill fall an averlILO'OQjeet the Yair te'iniperature may'be quite low, "s a'y. about 25 Fahrenheit Now the thermistor T-`3` will steadily respond to a 'cooler ,outside'air tO peratnre-.td unbalancen the bridge circuit (Figzm inaeiitotioii to cette' moeite of the'V Aooiii siiie'lir pathandpossibly some'opening of the side'airV 1'oat h. f By the time the aircraft has freeciiedl 103000 reet theiiow .oontroi valve is eijr'eadyin a 'position' to effect proper cabin air temperature. orfneariy so. Any further'edius'tments yviiigbe ffeoted by the bridge signals originating vin therr'ristors Tf-I andT-2- These two theriiiistorsbeing similarin characteristics andbeing t the same 'location in the cabin. eottogetneitoeilfect'similarbridge signals in opposite legs of trie bridge vojiroiiit (seerig. zal. 'lhegcontrolunit U comprises two switcl'iingv relays REQ-fl and RE-,2 -tov control the seryomotor igndapoiafized rei'ayjRE-s which receives its actuating signal from the bridge circuit and by. its 'response thereto e'iects operation of the two switching relays. When the polarized relay 13E- i3 clo`s'e`s. ,toi the left, a power circuit throngh rthe relay contactor is completedto energize the ingrelayfRE-I. v.This latter V relay then ses o oiioiiittiii-ough iimit'swi'toh sWf-zto the tor Winding `W'"2 to connect the windingto theD. J. power and start the motor I running' in ne' direction. 'However if the polarized relay RS/ closes to the right the switchingrelay i'isjeiiergized to complete e power circuit gh switchy SWv-l v`to the rnoto'r winding I,' thus vstarting themotor to run inthe vother direction. VIn vorder to' reduce 'arcing at 'the V'cointact' fits ofthe poiatigee relay RE-s a'pair'of ers Clfad' rC--2 are"connected at 'one "terinmal'to'tlie respective relay'contacts, and the other terminals are connected together 'and 'thrugh `a resistor 12x-'3 are connected tothe vvino ablecentactorfof relay RE-3. Also a'pair of 'resistors R`|a`ndR`2 ar'econne'c'ted across the 'windings ofswitching relays RE-*I and RIE-2 res'pectiyely for theA purpose of absorbing sortie of the induced 'charge of these windings upon break'- ving vof the vc'f` ntacts of the polarized relay.A Thus s'oie Vof 'this'selfi-'induced charge will be shorted throughJiSS'tOi's Rv--I valdl't--Z'and the resillt 'will 'be 'alInOSrt 'negligible rc'ng at the 'contacts iOvf teract the .c`h`ange in fresh air temperature.

jjofief Faereuiieitforeaoh iocoieet. Thus et s of 'fdiioiiig'tne voltage the' bridge eireuitto bedeeoriioed below. frite potentiometer 1=| (ipo ohms) "isj'iiier'ely'a Calibrating' unit tote need in 'ediustiiig'tiieioidg'eoifotiitmetten e'mennertiiat the pilots teiiiperature control` potentiometer P-2 of about 2'50 ohis value may indicate` an alpprox'iinate temperature range, for eXar'nple from y65" to 85 Iahreiiheit.V Asseen in Fig. 2c' Y the tntioirieters P -l` and P-2 are in thesameleg of th'ebridge circuit. The resistor in this 'saine leg ofwt'hebridge'is of 1"()0 ohms value and Iis needed to further increase the Ytotal resistance of this'p'ortion ofvthe circuit. The servoinotor follow-up potentiometer P- S naybe aboutllp olirns in value andis connected in series withthe entside airl thrniistor'Tf-LS "tol form one leg of the bridgeeirclfifit. A

The bridge circuit shown'irrFig.Y 2a 'isV part of vthe'f :oniple't'e circuit of'Fi'g 2 'and p royid'esV the means for energiz gilie'l polarized relay in such a rnanner thatvthe bridge outputiloy'vsin relay winding in either ef two'opp'osite d irectiejiisl depending on the actionof dther temperatnr'esensing resistors or th'erinisto'rs.A convenien c:e tlie bridgeV circuit inaybe considered as coinprisiig five legs fcnb, c, d 'and e, the latterlegrepi'esenting the relay `rcoil' `tQ beleiijefrgized bythe bridge output. For the bridge Vtolte balance;the total resistance of leg a should eeualthatef leg b and the y resistance oflegc shiiildequalthat o` f l`e g d. Now the two 'elidsof' lege willbe eonnectedto edili-potential points'fand noYcurrentl will flowin the Winding, O f relerj RETS- Hprfever' .if .th Cabin .fmpeffifebld' w'fieei'eeeejihe sistance ofwlegs L and@4 will decrease. cau ng more current tojilew -in lefg's a aridi/A than in legs b and c re'specltiyely. 'Now crrentwillnowmin leg e 'in one diree'tio`nlt-ov aetuate the relay crontactor in'onedirectionfac "ngly, adthus close a circuit to one otlie switching relays RE- f or REQ. This niet mioiie'tte eetmeter l in sucha d irec'tiona's'ktoause the flowcontrol .vali/@ te' Suppl'ymefeeld 'eilo ilbeliint the Same time theffQllOW.' eeentigletr P.-3.fi11 be loperated by the ervornotjor in such a' direction .as to decreesebe esterif Q f l'fid'elele Cfvfus making th? ress-al? PUS C fdqlilelfe' tually. .Nowt'he'only source of bridge'jnbalance is the diierence inresistce o'fmle'gsi a and'b `but this will he oy'e'reome Ia'tfs s' on` as thecabin air temperature' hasfbeefn Ip u'iie'e 'cow-n Vto 'etre-eet level, and thev resistance rof'l'eg" afisnow ledu'al to the resistance'ofllegnb."Ihus itma'y be seen that vthe twofcabinthermistfs work together to pro'- videna double bridgeun lanciiigdf'fectto lgire a lincre eie'c't'ive actionfofnthe polarized Vrelay RE-3. but theV bridge' wi'iriotfoo'iiiteiy febaiatio'e 'iiiitii the "tiie'iistor 'fr-z "has 'been affected by thelcliahged teniperature Vtliatthe system is vvcallingfor.` '(flferse thepo'l'v'rized relay will' 'rspend"tqclrrents fopposite d' ec- 'tion of"ow 'to"ove wthe Vrelayfcontactr' @een itis.iiyifey'tvienithwh d usually' includingia prerit'rn'agnet toproyi'de a reference field.

For a Adescription ofthe low. control valve in its preferred form reference is made to Figs. 3 and 4.. The valve Abody comprises the straightthrough cold S'de'sect'ion IU, the rass ilow control section ll'fo'r the' hotsiie,A the temperature yresponsive hoteide sectiorf2 and thefseryo'r'otor section I a. L The.'etir'owe Agiaaiii cy indioate'points of eoiineo'tioiifortiieduofA, is endo as shown in Fig. 1 and also indicate the directions of air flow. Centrally of one'side the valve section I0 is enlarged at I to provide a passage from the straight-through cold sidesection YIl) into the mass ilow control section II, the'passage itself` being indicated in Figs. 3 and 4 at I4. The valve body sections Il), II and I2 are portions of a onepiece valve casting but the servomotor section I3 is secured to they valvebody by screws I5 which` pass through a plate-like support I6 on the valve body. The support I6 is supported and braced by a triangular gusset portion 4I'I and a mainconnecting plate portion I8.

Except for the side opening I4, ythe valve section I0 provides a straight-through passageway forming the so-called coldside of the valve. Just forwardly of the, side opening I4 thereis a but-l terfly damper or valve member IIS pivotally` mounted along a mid-linev axis as at2.. Pivots extend into the wall `of valve section III in opposite directions and the top-pivot extends upwardly through a circular boss 2I on the upper side of the valve section I0. The pivot carries an adjustable arm or lever 22 which is pivotally connected at 23 to a collar 24 mounted on a connecting rod 25 and normally abutting a nut 26 on the adjacent end of the rod. At the other end of the collar there isa long compression spring 21 which is carried on the rod 25 and extends to a pair of nuts 28 and 28' forming part of an adjustable connection between the rod anda head portion 25. Thus the overall length of the rod 25 may be adjusted to adapt the valve for various installations. The rod head portion f 25 is pivotally connected at 29 to a cam member 30 rotatable by means of the servomotor I about the vertical shaft 3I. It might be further noted that the valve 'section 'I0 vca rries at least two mounting flanges 32 and 32 whereby the'valve body may be secured'to a part of the aircraft. As seen in Fig. 3 the valve member I9 is in closed position, so that most of the compressed air would thus be routed through the side opening I4 and along the hot side ofthe control valve. `By rotating the valveI member I9 counterclockwise (Fig. 3) the cold side of the valve would become open. Total displacement of the valve member I9 from the position of Fig. 3 to a wide open posi-I tion will be through an angle of about 70?, as may be measured on the view. j y Y Now to consider the hot side of the valve which v is reached by way ofthe side opening I4, reference is made to Fig.4.v The opening I4 enters the valve body section II between opposite parallel walls 33 and 34 which are joined at the top by an arched Wall 35 and at the bottom by a. cover plate 3B secured in placebythreaded studs 31. The walls 33 and 34 are 4provided with axially aligned valve seats 38 and 39, whichopen into the interim pressure chamber 40. This chamber which branches below the arched wall 35 extends upwardly to the interior of body section I2. Cooperating with the circular valve seats 38 and 39 are -valve members 4I and 42 forming a balanced poppet valve. Between the valve members is a sleeve`43 which like the members 4I and 42 is fitted over a valve push rod 44 having three portions of diiferent diameters to provide suitable shoulders to properly locate the poppet members 4I and 42. By using a double poppet Valve or spool type valve the air pressure on one valve member is counterbalanced by the air pressure on thefother member and the valve Vis more stable, especially'at positions ap,1;iroe ic l i-V ing closed position.

Means att'heright hand and left'hand ends o f the rod 44 are adapted to` actuate the rod in opposite directions.. Secured to the bodysection II is Vcylindrical housing 45 having an `integral end wa1l4$ atthe Vfree end and having a separate end wall 47 whereit threadsrinto body section I I.

The end wall Veil is centrally apertured toprovide apush rod guide 48 for rod 44.` 4The push rod 44g connects.. inside housing ,45 with one end of an evacuated bellowsd havingtheother end se-` cured to the .wal .l `46, as at 5 0.` In the end wall 41 there ist xed a pressureinlettube 5I, so that the interim .chamber pressure will prevail within the bellows housing 45, in order to effect a collapsing movement of the bellows on increaseof the interim chamber pressure..A The bodysection I-I also carries a second housing l52 ofrcylindrical forml closed at the free end by a threaded cap53 members 4 I v and 42 andthe sleeve 43 inl xed posif tion on the rod. vAtitsJree end within the housing 52 the Vrod also carries a nut 5l to provide anabutment for a cup-shaped washer 58. The

washer is formed with a series of concentric.

shoulders each serving as a seat for one of -a se-.`

ries of coil springs 59,. 6|] and 6IA bearing at the opposite end of housing A,52 on` the end wall 54..- Thus it will |be seen thatthe compressionspringa 59, Iiand 5I tendto resist closing movement of the valve members 4I and 42.-while the bellowsA 49 `acts to partly close the valve when the interim chamber pressure rises. ThisV valve 4I, 42 which isiresponsive; to vinterim chamber. pressure onl the. hot side of .the ow controlvalve acts to regulate mass airfflowon-a heating cyclefto prevent overs-pressurization on increase of engine power or increasevin'pressure of" thefcompressor bleedl` air. Thus'the mass ilow control valve'helps to` prevent wasting engine compressor airby closing-` on increase' of` the interim .chamber pressure. While the-valve mayfnot necessarily close com` pletely=when the compressor isv speeded-up, it

will close sufficiently to maintain interim cham-f The mass" ber pressure more or :less constant. flow control valvev 4I,/ 42 acts asA an automatic metering device so that there will not besudden f and severe Variations: in the airzpressure at the inlet side of the hot" air regulating vValve at the upper end-of interim. pressure 4chamber 40.- This will enable theylatter 4valve,.:corresponding to l valve E of Fig; `1,.=to1. effect more reliable control.. over the `owrof hot air into, the duct Cv in rethe thermostats andthe-f` spense, to Aaction of servomotor l I The hot side. regulating .valve is enclosed withinthe valve body section I2 .and comprises an.

upward `extensionloi' the. walls forming interim pressure chamber 4U. walls are joined at :the upperv end by a top wall 62, while the parallel wallstherebelow are pro' vided with Yconcentric valve seats 33 and 64. The

left handend of the body section I2 is closed bya Through these elements there ismovably mountecla` valve stem FIO-,having areduced end portion 'I'gif-f The reduced1iporltion provides' atl the -left 75. hand end thereof. e a shoulder 'against which is? These spaced parallel seated a poppet valve x'rfernber 12 followed by a asecuring nut 14. Near the periphery vof valve member `13-there arefi-providcd "several"y guide ngers- 13 havingia slidingfit'avithin' the valvev seatffi64 and actingv to slidablysupport the free end fof the valve-l stem.V The: doublepop'petA valveY structure acts to balance the airpressures actingon fthe' valve and vprevent chattering or erratic-v valve-Iaction, especiallyat'lhigh `rates of air flow.

Outside fof the 'Valvebodyv section 12; the valve a: seat lfor a' coilspringffq tendingf-:to close :the

Valve- 12, V'I3 when thrust `is removed from' 4the stern 10. In order to-retainthe disk 15in place onf the Arod or stem -therefsfacrossepini-whichis madersecure-'by allowing it tof-"seat 'ina shallow recess-formed inthesiderof fthe: disk away-*from the spring`x I 6 1 The stem''l-ll includes'z a threaded section-111.. adjustablysecured a tubular 'roller carrierli,l which hasa rollen-19 rotatably!rnoun'tl-fY edonlther-free end1thereof-.-'=The-roller 19fis inY continuous `contactwith:.the-cam' aidriven by the" electric. servomotorzl-af-.As seen :in Figa'B thecam 30isimoreor less semicircular :insplan but is off motoritseli isasgear reductionzsection 83,. con'- I taininga-xtrain of gearsfforireducingthe motor` speed. to-`v theicam .sha'it,:84 so L thatv lmany lrevolutions of the;motor armaturelzwill.:be-required to produce a ysingletrevolution "of the .cam shaft 84.

The :exact speed ratio. Ybetween :the` motor :and

the .cam .shaftk is not critical butlmay Vbia/200v to l 1:

if. desired. :The ratioA chosen alsodependson the speed ofthe motorusedrin thesassembly. The. power supplied to v:the motor.dependsion.v what is available Abutffor most iai-rcraft'rinstallations the motor. may .be operated onA 24 .voltsD; .C, derived f from .the storage batterica The gear. reductionsection of theservomotor; structuremay alsolin,

clude the motor followfup Y.potentiometer l2-3 andthe two-limit switches SWf-i-l andSW-2 previouslyV described.. A

` l .S'iiniizbiro 'of operation The present air conditioning and pressurizing systemv for aircraft :cabinslrl-includes anenginei dri-ven; air acoxnpressorV fornsupplying-airi at elea` vatedfpressure and'.temperatureZ .-Theair', which J isonly :a .minor :part :off theltotal compressor.outa 1 forithefcoolingpath'with lits' expansion' turbine aY common servomotor lr.

put, is conducted to a flow control valveShaving tworair paths f therethrough-reach?pathfbeing under) control of aseparata regulating 1valve.in= eluded: in the ilow-v control .valve.lr As expla-ined abovethe valve I9 .controls .air flow alongfarcoldi.sY

air -path .into the cabin; lwhileathe* Valve: V'1.2; 13a

controls air ilow'alongahot air-'.patliin'to the' cabin. These samevalvesare designatedl and Ein Fig. 1...Also the valve4l; 42 ,(valveD'in Figc..

1),.maintains alconstant inlet pressure-at:theho airA regulating. valve', solthat the Volume of hot air:`

70.. positioning of the l hotV air 'regulating-.valvaflZ13.l

flowing to the cabinisdeterminedfsolelv'byfthe- This .-valve :1125,13 thus. provides va regulator4 hav-f ing linear characteristics negardlesszofachanging compressor output, or changing. pressure" upff streamlof, the hotair :velvet Aszmayfbefseeninl ui. .Theycam andpus lthe' serv'o'moto'r and'V thpoppetvalve $2, 'provideswhat.riiaylbetterrned a--lost motion actu- Fig. 4, the valve 4l, 4231s maintained in posi- TheI` b'al'anbe` between these opposing A-forces thus ter'idsy tof position' tl-i-is mas'sflow control 'valve '4 l,

presser outp'iit resultsingreateriaircraft speed andlthene'ei forliincreasedlflow offcold -air to coolvthe cabin'. A.Moreover the air-cycle 'employed and..otherimpedingielements' constitutes allmiting-factor onthezoutputrof"cold'airf -The coordinatedactio'of thejhotfside valve 72, 73 vandthe cold-side lvalve lEtis effectedV by The control circuit-for the servomotor vnasi-'been explained in detail above. YHowever the action oftheservomotor in providingv an overlap. effectlior the' valves shouldbe-I-nent'oned.H -T -he servornotor operates the Vcam 3D -through reduction gearing and-as seen in Fig. l

3 fhefod'ilrsfpiwted *2Q-.the @am awa. The valve I9 is now closed and valve,12'l3 `is partly counterclockwise""directiorto" ope'n the Same'.r i' This openinrnovement vo'fialv'e lB-"i's thus under way during' vthainal' 'closing' irio'vei'rient of'valve '12',` "13. TheA instant 'positions "ofFig; 3- will correspond inFig'lwt'orthe intersection of line :cyY i witloftheF11-"axis:l Now-fassuiningthatithe cam 3l)` is rotated: in cloclewi'seiv'direction'-, 'the hot side' valve'12-,'113 will-:open toward its-"maximum open state while* Inovenient *of' the-'rod :w25-*toward Y a positio`n--0f *align-Infant 'with' carniishaft f 3l -will merelyfcbmpress Lthe' spring-"N-faslthe -r'o'd slides side valve 12, 13 reaches-lsed--position-andthe can 10 fcont'inuesl rotatingcountercloekwise the I 9 'lc'ohtinue'sf "mov-ing' toward-maximum open po'- sition-.flrvlhe :l-ink-and-levei-lconnecting means beatingl 'connectionbetween theservomotor and the respective'."vvalvesE I91"andf'12,o13l.f l`Foreifecting` properradjustment of the tworegulating valves the lrespective'actuating rods; include Vrheans previously;,describedf'for-varying the eiective flrngth thereof:A Also the-aCtuating'arm-Hifor "valve i9- is ad-justably clarnpedfto:the.. valvepiv'ot 2 El; es showninflig. 31.1 =It;isunderstood;- that valve is has avhole; ,therethroughyorallowing-'some nir leakagehintthefclosed position.A in: order to in'ain` tainffthe expansion-Iturbine-of the cooling unit'giny p a `sta-te 0f continueus Operation for, reasons rra viouslrexelaine lThe sonnes aetriextendrhe @vacca ressure' infchainber 40 act'- 9d actuating arrangement of air leakage from the cabin andv since air leal;-

age at high altitudes is greatest, the overlap characteristics vof the valves for any installation should be worked out on the basis of maximum altitude conditions to be expected in normal operation of the aircraft. If the pressurization flow from the system s enough in the high'altitude condition, then operationof thevalve in the overlap range (line :ry of Fig. 1a) will also Abe satisfactory at the lower altitudes. Itis further emphasized that the arrangement of the ysystem andthe valve controlling the two-path air fionr through the system is such that'complete control is accomplished on the basis of Atemperature demand alone. Adequate pressurization flow is provided automatically but without Waste of any air from the engine air compressor. No pressureresponsive piloting or actuatingv device is required to maintain pressurizing air flow.

In closing, the most important features and advantages of the present air conditioning system are herewith enumerated as follows: l y

(l) The use of a thermostatically. controlled valve device to proportion air flow through and air flow by-passing the air cooling unit;

(2) The overlap relation of the hot side and cold side air regulating valves to maintain cabin pressurizing air flow at load points when thermal requirements indicate lower ows than actually are required to offset cabin leakage; n

(3) Maintenance of cabin pressurizing requirements on thev basis of temperature demand alone;

(4) The mass flow control valve in the hot side air path to maintain a constant `inlet air pressure on the hot side air regulating valve;

(5) Comparative simplicity, compactness and light weight of the complete system. n

The embodiments of the invention herein shown and described are to be regarded as illustrative only and it is to beunderstood that the invention is susceptible to variations, modifications and changes within the scope of the ap- L,

pended claims.

1 claim:

1. A flow control valve for use in a cabin air conditioning and pressurizing system for aircraft comprising, a hollow valve body provided with an air inlet opening and two air outlet openings, means providing a straight-through air passage from said air inlet opening to the first air outlet opening, means providing a side opening in said straight-through passage extending through said valve body to said second air outlet opening, a first valve means movably mounted adjacentto said second air outlet opening, ay second Tvalve means movably mounted adjacent to said iirst air outlet opening, a third valve means movably mounted between said side opening and saidifl-rst ivalve means, a servomotor secured to said valve body, actuating linkages connecting said servomotor and said first and second valve means to provide simultaneous actuation thereof in' response to operation of said servomotor and adapted to correlate the action of said rst and second valve means in a. manner to initiate opening of either valve means before the other valve means has reached closed position, a spring tending to maintain said third valve means in open position, and fluid pressure responsive means subject to the air pressure in the chamber between said first and third valve means tending to close said third valve means on increase of pressure in said chamber.

2. A flow `control valve for use in a cabin air conditioning and pressurizing system for aircraft comprising, a hollow valve body provided with an airinlet opening for connection to a source of air at elevated pressure and temperature and also provided with two air outlet openings for connection to a cold air path including an air cooling unit and to a hot air path bypassing said air cool-- ing unit, means providing a straight-through air passage from Lsaid air inlet opening to the first airroutlet opening, means providing a side opening in said straight-through passage extending through said valve body to the second air outlet opening, a poppet valve movably mounted adjacent to said second air outlet opening, a butterfly valve moi/ably mounted adjacent to said rst air outlet opening, aser-vomotor secured to said valve body, actuating linkages connecting said servomotor and saidpoppet valve and butterfly valve to provide simultaneous actuation thereof in response to operation of said servomotor and adapted to correlate the actionv of said valves in a manner to initiate opening of either valve be,.- fore the other valve has reached closed position, in order to maintain a minimal air flow through vsaid valve body forpressurizng the cabin.

3. A flow control valve for use in a cabin air conditioning and pressurizing system for aircraft comprising, a hollow valve body providedwith an air inlet openingfor connection to a source o f air at elevated pressure land temperature and also provided with two air `outlet openings for connection to a cold air path including an air cooling unit and a hot air path bypassing said air cooling unit, means providing a straight-through air passage from said air inlet opening to the first Vair outlet opening, means providing a side opening in said straight-through passage extending through said valve body to the second air outlet opening, avpoppet valve movably mounted adjacent to said second air outlet opening, a butterfly valve niovably mounted adjacent to said first air outlet opening, a reversible servomotor secured to said valve body, an actuating connection between said servomotor and said poppet valve for moving said poppet valve gradually from open to closed position on operation of said servomotor through a predetermined range in one direction, an actuating connection between said servomotor and said butterfly valve for moving said butterily valve gradually from open to closed position on operation of said servomotor through a predetermined range in the other direction, and said actuating connections providing an overlap of said predetermined ranges of operation of said yservomotor during which both valves are partly open in order to insure a minimal air flow for pressurizing the aircraft cabin. l

4. A flow control valve fas recited in claim 3 including a valve means having a movably mounted valve member between said side opening and said poppet valve, a spring tending to mainavisame condition-ing an'df pi'ess/urlaingsystemY for 'aircraft comprising, faf=hollow =valvebody provided-with falso providedrwith -itwo` air outl'et openings for f connection to a cold air path inc'lud-ing'anfair .-cooling unit'a'nd` to V'ahot air path bypassing said iaincooling unit,.means lproviding. a straight- -through air -passage'fromsaid air inlet opening Eto the first air outlet openinggmea-n's' providing a I side opening: in said straight-through' passage extendingthrough said :valve body: to the second lair Voutlet opening,r a .poppet'valve movab'ly ymounted adjacent to saidxsecond 'air outlet opening, av butterfly 'valveem'ovably` mounted v'adj acent #to Ysaid irst airoutletfopening, alreversible servomotorx-secured l.to said-'valveV body,` acampper- Zat'edfby said-'servomotor and y:having a cam i ace foroperativeengagement `by a vcam follower-connected to said. poppet valve,i'spring means 'tending-to. close vsaid poppet 4valve vand :maintaining l:said cam follower in engagement with said cam ."face 'until the contour thereof 'allows saidlpoppet .valve to reach closedrpos'ition, a crank ypin mount- 'edontsaid cam, a link .and lever connectionr beftWeen-saidcrank pin and said buttery valvein- :cluding `lost motion meansbetween said` link vand lever, the positioning. ofs'aid .crank pin and the 'contour of said camriacebeing '-.such asto' provide :for 'onedire'ction of cam. rotationa rst z range of cammovements durin'g 'which said' ipoppet valveis movedfromiull'open position'toward closed position While said butterfly valvefremains clo'sed, a second rangeof cam; movement` during v'which said-poppetfvalve is further moved l.toward vclosed position while-said'butteriiy'valve'is moved toward'open position, Aand a third rangefofzcam 'movement-.during which 'saidl butteriiyv valveis "moved to full open :position whilefsaid poppet valve remains closed.

6.y Ailow control vvalve `for use in. a cabin-air lconditioning and-pressurizing system- '-for.,` air- =craft comprising, a `hollow valve Vbody provided 'with an air inlet-opening and two air' outletopenings, means `vproviding a iirstvpassage from said air Iinlet opening 'to the iirstairoutlet. opening, means providing a -second passage lextending through said `valve body from said rstpassage to said second air 4outlet opening, a rstvalve means movably mounted radjacent lto 1 saidfsecond airputlet-.Opening a second valve means movably irnounted adjacent ltor-said first -air outIetopening,

a Ireversible `servoniotor secured to-fsaid. valve =.body, a lost motionlactuating-'connectionfb'etween 'said servomotor and-said. firstivalve. means for -moving said first valveimeans gradually .from 'open to closed'positiononoperation of said servofrnotor through a predetermined. range in one direction, a lost motion actuating connectionbetween said vservomotorandsaid. .secondi valve l'means for moving said second valve Vmeans grad- V'ually from open to lclosedu'positionlon* operation fio is 7.5 AAfifloi'vcontrolftvalve' as Y'recited lin claim-6 'including a thirdv valve-"means having 'afinovably fmount'ed valveineinbermcated in saidlsecond passage, as'pring tending-to inaintain said valve kmemberf'inthe -open position; andfluid pressure responsive-means subject to;the lair' pressure in 'the portion -of said -secondpa'ssage between said first and-third valvel means tending to close said 4moi/ably -mounted valve member on increaseof pressure in said portion of said second passage.

-8. A cabinair conditioning andpressurizing "system for aircraft comprising, an air compressor vvfor providing a' source of air-atelevated pressure and tempera-ture, means connectedto saidf source fof air to 'subdivide said vair for` passage toward the vcabin along a hot 'ain conduit Vand la 'cold-"air conduitfan air cooling-unit i-nterposedin'said Acold '-air 'conduit tofco'ol'the air flowing lfrom said 'source of 'air through saidcold air conduittovwardv the cabin; means to mix the' 'air traversing said'hot airconduit' andsaid col-:lair conduit before the combined Aiiow enters the cabin, ailrst valve means to rdetermine the' rat'efofair 'flow "along r`said hot airconduit, a'second valveA means toI determine the rate Aof air iioiv-along'said cold air conduit; a'reversible'servomotor for actuating said first 'ar'ids'econdv valve'im'eans, aflost vmotion 'actuating connectionI between' said servoinotor and said rst'valVe means`- forv gradually clos'ing said rst'Valve-means onloperation -of said servomotor through a predetermined vrangeliny one direction; -a lost motion actuating f connection between fsaiddservomotor `and '-said second Avalve means I iorg-raduallywclosing said` second. valve means on operation `ofs'aid Js ervomotor through a predetermined range'in the other direction, said actuating connections providing' an. :overlap i of saidpredetermined `ranges of -operation of Asaid lservomotor lduringlfwhich both A'valve-"means are partly open in order to insure a minimal airflow for pressurizing the aircraftl cabin andtheflost motion in1'said=actuating connections providing free movement of either valve means-toward full open position afterooinplete closing ofthe other Valve means.

-9^ A cabin; air conditioning. and pressurizing 'systemffor'aircraft as recitedin'claim 8 and further comprising athird valve :means `having a movablv mounted valve 'member located insaid hot air conduit-betweenfsaid means to subdivide said air and said iirst valve means, a springztending to maintain said valve member iii-the open `position, .and fluid pressure responsive means subject tol'theain pressure inrthe portion of said ihot'airlconduitbetweensaid irst and third valve .means tending to. close 'said' movably mounted Cvalvevmember'onincrease of pressure in said por- -tion offsaida hot air conduit.

WILLIAMlVI. HYNES,

REFERENCES CITED 'The following referencesare of record inthe -leof thisV patent: l l

' UNITED STATES PATENTS Number Name Date 2,194,749 Gregg Mar. 26,1940 y 2,350,896 Jde June 6, 1Q44 A2,401,861 Cunningham June 11,'1946 2,474,441 Sparrow June 28, 1949 

